Using the fileFilter parameter

If the file filter is not a null string, it is interpreted as a list of one or more regular expressions which is tested against each file name.

For example, a fileFilter value of 'txt' would match with 'Test.txt' but would also match with 'SometxtFile.doc'. To match with '.txt' you would need to add a a dot, but even then a filter of ".txt" would be interpreted as [any-character]txt. You need to add an escape character "\" before the dot to specify it as a literal match. Note that if your literal string does not have an @ sign in front of it, you will need to use two consecutive \. For example "\\.txt" or @"\.txt" are the same (and "\.txt" will not compile).

Note that "\.txt" would still match a file such as "file.txtold" or "file.txt.old", so you can append the $ specifier which matches with the end of the string: e.g "\.txt$" to ensure you only match files with the last extension as .txt

Multiple regular expressions are separated with a semicolon (";"). Each one can be an inclusion or exclusion. Exclusions start with a minus sign ("-").
Inclusions may start with an optional plus sign ("+"). Some examples :

Each item in your filter is matched against the entire filename including drive and full folder path. Do not start an entry with a caret ("^") unless matching the full path string. To match a complete filename (within a folder), use a folder separator (a backslash). Because the backslash is also the escape character it must be entered twice.

string fileFilter = @"\\LogFile.txt$"; // Matches a file called LogFile.txt but not SomeOtherLogFile.txt
string fileFilter = "\\\\LogFile.txt$"; // Same as above but without the @ sign

Create a zip with FastZip using progress events

You can set events which will fire on each file. This gives you the opportunity to display a progress notification, and to decide whether to stop.

How to extract a Zip File using FastZip with Name Filter and Confirm Overwrite

using System;
using System.Windows.Forms;
using ICSharpCode.SharpZipLib.Core;
using ICSharpCode.SharpZipLib.Zip;
private bool _stop;
public void TestFastZipUnpack(string zipFileName, string targetDir) {
// Set the method that will be called on each file before extraction but after the OverwritePrompt (if applicable)
FastZipEvents events = new FastZipEvents();
events.ProcessFile = ProcessFileMethod;
FastZip fastZip = new FastZip(events);
// To conditionally extract files in FastZip, use the fileFilter and directoryFilter arguments.
// The filter is a list of regex values separated with semi-colon. An entry starting with - is an exclusion.
// See the NameFilter class for more details.
// The following expression includes all name ending in '.dat' with the exception of 'dummy.dat'
string fileFilter = @"+\.dat$;-^dummy\.dat$";
string directoryFilter = null;
bool restoreDateTime = true;
// Will prompt to overwrite if target filenames already exist
fastZip.ExtractZip(zipFileName, targetDir, FastZip.Overwrite.Prompt, OverwritePrompt,
fileFilter, directoryFilter, restoreDateTime);
}
private bool OverwritePrompt(string fileName) {
// In this method you can choose whether to overwrite a file.
DialogResult dr = MessageBox.Show("Overwrite " + fileName, "Overwrite?", MessageBoxButtons.YesNoCancel);
if (dr == DialogResult.Cancel) {
_stop = true;
// Must return true if we want to abort processing, so that the ProcessFileMethod will be called.
// When the ProcessFileMethod sets ContinueRunning false, processing will immediately stop.
return true;
}
return dr == DialogResult.Yes;
}
private void ProcessFileMethod(object sender, ScanEventArgs args) {
string fileName = args.Name;
// To stop all further processing, set args.ContinueRunning = false
if (_stop) {
args.ContinueRunning = false;
}
}

VB

Imports ICSharpCode.SharpZipLib.Zip
Imports ICSharpCode.SharpZipLib.Core
Imports System.Windows.Forms
Dim _stop As Boolean
Public Sub TestFastZipUnpack(ByVal zipFileName As String, ByVal targetDir As String)
Dim events As FastZipEvents = New FastZipEvents()
events.ProcessFile = AddressOf ProcessFileMethod
Dim fastZip As FastZip = New FastZip(events)
' The only way to conditionally extraxt files in FastZip is to use the fileFilter and directoryFilter arguments.
' The filter is a list of regex values separated with semi-colon. An entry starting with - is an exclusion.
' See the NameFilter class for more examples.
' The following expression includes all name ending in '.dat' with the exception of 'dummy.dat'
Dim fileFilter As String = "+\.dat$;-^dummy\.dat$"
Dim directoryFilter As String = Nothing
Dim restoreDateTime As Boolean = True
' Will prompt to overwrite if target filenames already exist
fastZip.ExtractZip(zipFileName, targetDir, fastZip.Overwrite.Prompt, AddressOf OverwritePrompt, _
fileFilter, directoryFilter, restoreDateTime)
End Sub
Private Function OverwritePrompt(ByVal fileName As String) As Boolean
' In this method you can choose whether to overwrite a file.
Dim dr As DialogResult = MessageBox.Show("Overwrite " + fileName, "Overwrite?", MessageBoxButtons.YesNoCancel)
If (dr = DialogResult.Cancel) Then
_stop = True
' Must return true if we want to abort processing, so that the ProcessFileMethod will be called.
' When the ProcessFileMethod sets ContinueRunning false, processing will immediately stop.
Return True
End If
Return dr = DialogResult.Yes
End Function
Private Sub ProcessFileMethod(ByVal sender As Object, ByVal args As ScanEventArgs)
Dim fileName As String = args.Name
' To stop all further processing, set args.ContinueRunning = false
If (_stop) Then
args.ContinueRunning = False
End If
End Sub